Device Design And Experimental Study On Two Dimensional Vibration Aging Residual Stress

Under the effect of the external cyclic stress,the residual compressive stress around the hole which is treated by the cold extrusion of split sleeve will be attenuate,and would reduce the fatigue resistance of the structure.However,due to lack of understanding of the law of stress attenuation,people can not accurately evaluate its impact.Therefore,a two dimensional vibration stress release method is proposed to study the stress release around the fastening holes(mainly on aluminium alloy)strengthened by cold extrusion of slotted bushes.The main work and results was as follows:1.The theoretical study on the realization of two dimensional vibration was carried out.Double excitation was selected to realize the two dimensional vibration.The parameters of the two dimensional moving trajectories were analyzed in detail,the two perpendicular harmonic vibration with equal amplitude,90-degree phase difference is proved to synthesize the two dimensional vibration effectively.Analyzed by Matlab simulation,the amplitude of the two excitation directions affects the size of the trajectory while the vibration phase difference affects the shape of the trajectory.2.The research of vibration device design was carried out.The design and selection principle of ultrasonic vibrator was discussed;the structure of parallel circular flexible hinge was optimized by flexibility analysis;combined with the experimental requirements,the positioning and control of the workpiece and the two dimensional vibration system in the two dimensional vibration device were introduced,and the construction of the two dimensional vibration device platform was finally completed.3.The simulation analysis and vibration characteristics detection of the two dimensional vibration system was carried out.The various parts of the device were analyzed by using Ansys Workbench software to further optimize the parameters of design;the natural frequency and the vibration amplitude of the ultrasonic transducer,the ultrasonic vibrator and the two dimensional vibration system were detected by using the PSV doppler laser vibrator.The two dimensional vibration system test results show that when 50 V excitation voltage is applied to the ultrasonic oscillator 1 and 2 separately in system coordinates,the amplitude response in Y direction reach 5μm and 4.8μm,and in X direction both could reach 100 nm.Compared with the vibration in Y direction,the vibration in X direction is slight,which verifies the validity of the two dimensional vibration system.4.The stress release experiment of the two dimensional vibration method for the cold extrusion hole was carried out.The residual stress around the hole before and after the cold extrusion and the two dimensional vibration were measured by X-ray diffractometer.After comparison,it is found that the average stress relief rate reaches 22.6%,the maximum reaches 32.2%,the average stress relief rate at the peak reaches 32.0% and the maximum reaches 46.9% in the 5mm range of hole edge treated by two dimensional vibration method,and the range of stress reduction is mainly within 0~5 mm from the hole wall of workpiece,which is basically consistent with the range of cold extrusion strengthening,therefore the effect of two dimensional vibration aging on stress release in the cold extrusion strengthening area is significant.By analyzing the orthogonal experimental data,it is found that the phase difference is the most important factor affecting the effectiveness of two dimensional vibration aging.